Barnum et al. U.S. Pat. No. 6,671,577, Dec. 30, 2003, describes a system and method for directly connecting an ISS advanced facer canceler system (IAFCS) to a DBCS/OSS. Limitations of this system are described in commonly assigned Redford et al. U.S. Patent Publication No. 20050247606, Nov. 10, 2005, the contents of which are incorporated by reference herein for all purposes. Redford et al. describes a sorting system using multiple sorters operating as part of a single, multi-sorting machine unified system. The '606 system includes a plurality of input sections capable of operating in parallel, each including a feeder that takes in mail pieces one at a time and a scanner that scans each mail piece for destination indicia, a plurality of stackers each comprising at least one row of pockets, a control system that determines a destination pocket in the stacker for each mail piece based on a predetermined sort scheme and the destination indicia, and a routing system effective to route mail in accordance with the sort scheme from any input section to any pocket of a stacker.
The routing section of the '606 publication relies in part on crossover sections where a mail piece being conveyed from one input section to a stacker crosses over (passes through) another conveyor. Such a crossover function increases the likelihood of contention between mail pieces at the intersection of the conveyor paths. The present invention seeks to increases performance in a multi-machine sorting system of the kind described in the '606 publication by reducing the quantity of mail that must be rejected due to situations in which mail needs to be sent simultaneously to the same path. This increases the effective overall throughput of the system is and reduces the amount of mail that must be fed again.